Sebastian Vettel will start his first race for Aston Martin at the back of the grid after being hit with a penalty at the Bahrain Grand Prix.

Vettel has been penalised for ignoring yellow flags in qualifying at the Bahrain International Circuit in Sakhir on Saturday.

The four-time Formula One world champion breached the rules when Haas driver Nikita Mazepin spun at Turn 1 during Q1, resulting in double waving of yellow flags - which Vettel failed to respect.

Vettel qualified in 18th but was given a five-place penalty and hit with three penalty points after being summoned to the stewards ahead of Sunday's race.

The stewards said in their verdict: "[Valtteri] Bottas, Vettel, [Sergio] Perez and [George] Russell approached the scene and drove past Mazepin. Bottas, was immediately instructed by his team to abort his lap in accordance with the Race Director's Event Notes.

"Perez and Russell had received the chequered flag, and were instructed to slow, with Russell receiving the additional information that it had been a double yellow sector.

"Vettel did not abandon his lap. He explained to the stewards that he saw the smoke ahead of him, but was unsure if it was a lock-up or a stopped car until he was quite close to the car and the smoke was lifting.

"The stewards observed that he had already passed the signal panel when it illuminated as he approached the scene, and that the marshals in that turn had not yet reacted with a yellow flag. Nevertheless, Vettel was approaching a car that was stopped sideways on the track and by the rule this would necessitate a double yellow flag."

Vettel said: "We were already quite far back so it doesn't make a difference.

"Hopefully we will come up with something clever with strategy so we can move up and enjoy it along the way."

Lewis Hamilton claims it is "no secret" the new Formula One regulations have been introduced to slow Mercedes, but he was encouraged by their opening qualifying session of the season.

Changes to aerodynamic regulations for 2021 have had a great impact on the reigning champions' low-rake chassis, the Silver Arrows say.

Mercedes have won the past seven constructors' championships, yet Red Bull led the way in pre-season testing.

The fastest lap belonged to Max Verstappen and the same man took pole on Saturday at the season-opening Bahrain Grand Prix.

But Hamilton was only 0.388 seconds back in second and that performance spells good news for the Briton, with all 16 Bahrain winners coming from the first two rows of the grid but only seven of them qualifying on pole.

Meanwhile, Verstappen has retired three times at this event and four times at the Sakhir track.

Hamilton remains very much in contention, despite feeling the rules have been designed to hurt his team.

"It's no secret. The changes, of course they've been done to peg us back," he said. "We've had the changes last year to our engine to do the same thing.

"That's okay. We love a challenge, we don't look down on these things. We just work hard to do the best that we can, and that's what we'll do."

But Hamilton was not amused by a request for him to analyse where Red Bull are now better, as Verstappen - having ended last year with a win - targets back-to-back triumphs for the first time in his career.

"Really? I don't want to tell you what our problem is," Hamilton said. "They're just faster."

With Silver Arrows team-mate Valtteri Bottas qualifying third, the top three - Verstappen, Hamilton, Bottas - are on course to become the first trio to appear on 15 podiums together.

Although Verstappen is still in the lead, this Mercedes challenge seemed improbable for Hamilton just days ago.

"I think this is a really good step forward for us coming this weekend," he said.

"We thought it was double the gap that you see today. That's down to some really fantastic work from the men and women back at the factory.

"Of course we want to be first, but we knew that it was going to be a challenge, we knew from day one on track really that Red Bull was going to be faster than us.

"We knew we had a bit of an uphill slope to climb. I'm just proud of everyone's efforts."

Elsewhere, two former champions had vastly contrasting fortunes after offseason moves.

Three-time Bahrain winner Fernando Alonso is back in F1 with Alpine Team, formerly Renault, where he won two world titles.

And his second debut was a success as he reached Q3 for the first time since Monaco 2018 and claimed ninth on the grid.

"It was good," said Alonso, who won this event on the previous two occasions it opened a season. "I think we have to be pleased with the qualifying.

"I was not confident in any of the sessions so far in the weekend - I was struggling a little bit to feel the rear of the car in windy conditions - and now in the qualifying everything was calmer.

"The night situation I think helped us with the cooler temperatures, so I was able to attack and feel the car a little bit better and it was fun."

On the other hand, Sebastian Vettel was eliminated in Q1 as his second run was hampered by yellow flags prompted by Haas rookie Nikita Mazepin's spin.

No driver has more wins (four) or poles (three) in Bahrain than the former Ferrari man, but his Aston Martin bow did not go to plan.

Vettel will start from 18th and said: "If I panicked now, would it help? If I was really upset?

"For sure, I am upset and angry that it wasn't our fault in a way not to make it through, but we have to take it and do what we can, preparing tomorrow."

Matters could yet get worse for the German, who will appear before the stewards on Sunday for failing to respect the flags, potentially meaning a five-place penalty.

Sebastian Vettel is excited to get the 2021 Formula One season underway with Aston Martin, with the former world champion seeing plenty of potential at his new team.

Vettel, a four-time F1 champion, left Ferrari at the end of the 2020 campaign, bringing an end to a six-season stint with the Italian manufacturers.

Charles Leclerc had usurped him as Ferrari's number one driver, and Vettel slumped to a 13th-placed finish in last year's drivers' standings, claiming just one podium finish.

Vettel has now switched to Aston Martin, who have rebranded the Racing Point team to make their F1 return after a 61-year break from the competition. 

The German made no secret of his disappointment at how his final season at Ferrari panned out but is anticipating an exciting debut year with Aston Martin.

"I am not happy with last year in terms of performance – partly my performance – but I accepted it," said Vettel at the unveiling of the AMR21 car on Wednesday, which also featured NFL great Tom Brady and Hollywood star Daniel Craig.

"There are things that didn't go well, but I am looking forward to this year.

"I go racing to win and obviously it's a very exciting project, a new start and a new chapter for the entire team. I'm very much looking forward to it.

"Winning is maybe a bit ambitious straight away, but it's everybody's goal, it's why we go racing.

"Even though I have raced for four Formula One teams and for many years, starting a new season with a new team still gives me a sense of excitement.

"I see potential. I think the team has always been very successful in the past with limited resources, now the regulations in F1 are changing, and with the new launch of Aston Martin coming back, a lot of talented people joining and coming together to this already good group already, I think it's [his arrival is] only an addition.

"So I hope that I can contribute as well, and I think if we keep sharing that joy and passion then good things will follow."

Vettel's Ferrari future was decided before the 2020 season – which was derailed due to the COVID-19 pandemic – had started, yet he claims to have had no doubt that Aston Martin was the right move. 

"As a driver, I have always kept my eye on the competition and this team has consistently impressed me with what they have been able to do without the biggest of budgets," he added.

"So, when Lawrence [Stroll] and Otmar [Szafnauer] approached me last year, and explained what their ambitions were, I was immediately very motivated to join the team.
 
"I love the history of motor racing and Aston Martin is one of the great names of the past, so it is fun to be part of their return to Formula One after an absence of 61 years.  
 
"I have not driven the car yet but I think it looks great. I am really looking forward to getting it out on the track. I am also looking forward to working with and getting to know better everyone in the team, including my team-mate Lance [Stroll]. We will certainly make a big effort to deliver some good results together and have fun doing it."